Mold of composite metal

ABSTRACT

A LAMINATED MOLDING TOOL ESPECIALLY ADAPTED FOR PUNCH MOLDING COMPRISING A MOLDING SURFACE LAYER OF NICKEL INITIMATELY BONDED TO A SUPPORTING SUBSTRATE COMPRISING AN ALLOY OF ALUMINUM AND ZINC WHICH SUBSTRATE IMPARTS RIGIDITY AND STRENGTH TO THE MOLDING SURFACE LAYER

H. A. JAHN LE MOLD OF COMPOSITE METAL Jan. 12, 1971 Filed Dec. 23, 1968Fig. 2

INVENTOR.

HERBERT A. JAHNLE ATTORNEY United States Patent 3,554,711 MOLD 0FCOMPOSITE METAL Herbert A. Jahnle, Havertown, Pa., assignor to The BuddCompany, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 23,1968, Ser. No. 785,965 Int. Cl. B21c 3/16 US. Cl. 29197 5 ClaimsABSTRACT OF THE DISCLOSURE A laminated molding tool especially adaptedfor punch molding comprising a molding surfacelayer of nickel intimatelybonded to a supporting substrate comprising an alloy of aluminum andzinc which substrate imparts rigidity and strength to the moldingsurface layer.

BACKGROUND OF THE INVENTION This application is related to anotherapplication of the same inventor entitled Laminated Molding Tool, filedsimultaneously herewith and involving a different alloy substratematerial than that of this application.

Recently, molding tools having a nickel molding surface have come intowide use. These molding tools take the form of male, convex punch moldsor female, concave molds. A wide variety of shaped plastic and metalarticles may be formed utilizing these punches and molds. Nickel is adesirable molding surface for these tools due to its availability,strength, thermal properties, etc.

More recently, electroforming methods have been developed formanufacturing these nickel punches and molds. Generally, the moldingtools are formed by electrodepositing nickel over a removable mandrelcomposed of a reinforced plastic, cast or machined metal in the shape ofp the desired molding tool. The mandrel is then removed from theelectrodeposited nickel layer, yielding a molding surface in the desiredshape.

It has also been proposed to back-up or support the electrodepositednickel molding surface layer with an inexpensive reinforcing material toprovide substance, strength and thermal properties thereto. Severalbothersome problems have arisen, however, in connection with providing asuitable supporting substrate for nickel molding surfaces. Thesereinforcing or supporting substrates are generally laminated or bondedto the nickel molding surface by pouring the reinforcing material intothe formed nickel mold in molten form and allowing the composite tool tocool. If the melting temperature of the reinforcing materiay is toohigh, however, the nickel molding surface layer will melt and deformwhen the molten reinforcing material is too high, however, the nickelmolding surface of the reinforcing material is too low, the number ofuses to which the supported nickel molding tool can be put is severelylimited. That is, in many molding operations, the punch or mold tool issubjected to extreme temperatures. If the reinforcing material has toolow a melting point, the tool may be deformed due to melting of thereinforcing material during such elevated temperature moldingoperations.

In addition to having thermal properties compatible with the nickelmolding surface and high temperature molding operations, it is necessarythat the reinforcing material have a high degree of strength in order toproperly reinforce the nickel molding surface during the moldingoperation. This is particularly true with respect to male or convexpunch molds wherein the tools are subjected to a high degree ofcompression. It is necessary not only that the reinforcing material havea high degree of compressive strength in order to avoid deformation ofice the tool during molding operations, but also that it not be brittlein order to avoid chipping or cracking of the tool during operation.

Moreover, it is necessary that the reinforcing material have goodWetting and bonding properties with respect to the nickel moldingsurface layer. In other words, the reinforcing material must be selectedso that upon cooling of the molten material after it has been insertedin the nickel molding surface, a strong bond will result between thereinforcing material and the nickel molding surface in order to avoidsubsequent delamination during the molding operation to which it issubjected.

Heretofore, reinforcing or supporting substrates for nickel,particularly electrodeposited nickel molding surfaces, having meltingpoints compatible with nickel and the intended molding operation, goodmechanical strength, particularly compressive strength and satisfactorywetting and bonding characteristics have been unavailable.

In nickel plated tools, the surface may become worn or damaged. In thesecases, it is desirable to resurface the tools by Welding, for example.This requires substrate materials which are capable of being used in thewelding operation.

It is often necessary to mechanically attach or mount nickel platedtools to other mechanical elements. This may require drilling orthreading the substrate material, which must be capable of withstandingthis treatment.

It is an object of the present invention to provide a laminated moldingtool comprising a nickel molding surface layer intimately bonded to athermally conducting, supporting substrate which imparts rigidity andstrength to said nickel molding surface layer.

It is a further object of the present invention to provide a moldingtool comprising a nickel molding surface laminated to a supportingsubstrate wherein the material comprising said supporting substrate hasa melting point compatible with the melting point of nickel and hightemperature molding operations.

It is a further object of the present invention to provide a laminatedmolding tool comprising a nickel molding surface bonded to a supportingsubstrate wherein the material comprising said supporting substrate hasa high degree of mechanical strength, particularly, compressivestrength.

It is a further object of the present invention to provide a moldingtool comprising a nickel molding surface bonded to a supportingsubstrate wherein the material comprising said supporting substrate isintimately and strongly bonded to said nickel molding surface.

It is a further object of this invention to provide a backup materialfor a nickel shell which is capable of being mechanically attached toother elements by means of threaded screws, etc.

It is still a further object of this invention to provide an improvednickel plated tool which is easily repaired 1f the nickel surfacebecomes worn or damaged.

SUMMARY OF THE INVENTION It has been found that these and other objectsmay be realized according to the present invention by utilizing as asupporting substrate for a nickel molding surface in a laminated moldingtool an alloy of aluminum and zinc wherein the amount of aluminum is inthe range of from about 10% to about 30% by weight.

It has been found that the above described alloy combines the bestproperties of melting point, mechanical strength and lamination tonickel surfaces.

Molding tools comprising nickel, particularly electro deposited nickel,laminated to supporting substrates comprising the above described alloyshave a high degree of mechanical strength and may be utilized in anymolding operation in which nickel molds are conventionally employedwhile avoiding delamtnatton, cracking, chipping, etc. or the moldingtool.

DETAILED DESCRIPTION OF THE INVENTION Other objects, features andadvantages of the invention will be apparent from the following detaileddescription and the accompany drawings, which are illustrative only, inwhich FIGS. 1 and 2 show convex. male molding tools in accordance withthe invention: and

FIG. 3 depicts a molding operation employing a convex, male molding tooland a female, concave mold of the invention.

With reference to the drawings, the molding tools 1 and 5 comprisenickel, preferably electrodeposited nickel. molding surfaces 2 and 7intimately bonded to supporting and reinforcing substrates 3 and 9comprising the above described alloys. Optionally, interlayers 4 and 8of copper may be interposed between and intimately bonded to the moldingsurfaces 2 and 7 and supporting substrates 3 and 9. These copperinterlayers are provided in the molding tool to enhance the bond betweenthe nickel molding surface and the reinforcing material. It is to beunderstood that the copper interlayer is only an optional feature of theinvention. The alloys comprising the support substrate form sufficientlystrong laminates with the nickel molding surface layers for mostconventional operations. The copper interlayers may be interposed in thetool where the latter is subjected to extremely rigorous moldingoperations.

In FIG. 3. a male, convex molding tool 1 and a female. concave mold 5are depicted. in a typical operation, the material 6 to be molded, i.e.,plastic, metal, etc. is placed in the concave mold 5. The desired moldedarticle is formed by punching or stamping the material contained in theconcave mold 5 with the convex molding tool 1. Alternatively, the moldsof the invention may be employed in conventional iItlEZCtlOl'l moldingoperations.

As will be apparent, many of such molding operations are carried out atextremely elevated temperatures. Accordingly, it is necessary that thereinforcing materials 3 and 9 of the convex and concave moldsrespectively, have sufficiently high melting points to withstand thesetemperatures without melting and/or deforming, thereby resulting indamage to the molds. On the other hand, it is necessary that thereinforcing material have a sutficiently low melting point in order thatit may be poured in molten form into the nickel molding surface layerwithout melting and/or deforming the latter. The alloy reinforcingmaterials of the present invention have melting points and thermalproperties compatible with the nickel molding surfaces with which theyare laminated, and, further, which are compatible with the temperaturesencountered in most molding operations.

The melting point of nickel is approximately I647 F. Obviously, themelting point of the alloy reinforcing material must be below thismelting point of nickel. As cautioned above, however, the melting pointof the reinforcing material must be above the temperatures normallyencountered during molding operations. Practically, reinforcingmaterials having a melting point below 750 F. are generally undesirable.Accordingly. the alloy reinforcing materials of the present inventionhave melting points in the range of above 750 F. The pre ferred backingor reinforcing, support material of the present invention comprises analuminum alloy which includes about 10% aluminum by weight, and zinc ofabout 80% by weight. This alloy has a melting point of approximately 896F. thereby rendering it suitable for pouring in molten form into aformed nickel molding surface layer without melting and/or deforming thelat ter, and, also, suitable for inclusion in a molding tOOl which isemployed in molding operations conducted at elevated temperatures. It isto be understood, however, that the percentage ot aluminum in the alloymay range 'ill .4 'rom about 10% to about by weight and that the .mountof zinc may be aried from about to about 0% by veight. If thesepercentages are increased or tecreased below the stated ranges, themelting point of .ne alloy tends to rise, thereby rendering itunsuitable "or a supporting substrate for nickel molding surfaces.

Furthermore, although any of the alloys defined by he recited percentageranges may be employed in the holds of the present invention. thepreferred alloy (20% or aluminum and of zinc) has been found to form inextremely strong bond or laminate with the nickel holding surface and toconstttute a reinforcing material raving a high degree of mechanicalstrength, particularly, .ompressive strength.

The following is a representative process whereby the molding tools ofthe present invention may be prepared. A nickel molding surface iselectrodeposited over a re- .novable mandrel having a shape conformingto the desired configuration of the resulting mold in a known manner.Following completion of the electrodeposition, :he mandrel is removedfrom the electrodeposited nickel molding surface. Although theelectrodeposition process 15 applicable to and while understanding thatthe present invention contemplates the formation of concave, femalemolds, t e electrodeposition process is more adaptable :o the depositionof metal on convex surfaces than on concave surfaces. The nickel may beelectrodeposited to any desired thickness. Generally, thicknesses fromabout 0.0005 inch to 0.5 inch are electrodeposited. Following removal ofthe mandrel, the nickel molding surface is iupported and moltenreinforcing material is poured therein. Preferably, the nickel moldingshell is first placed n a furnace and preheated generally to atemperature ust below the melting point of the reinforcing alloy to beadded. Also, preferably the nickel shell is first .zoated with a thinlayer of copper in order to improve he resulting bond between thereinforcing material and .he nickel shell. Further, a conventional fluxmaterial e.g., powdered aluminum-silicon brazing alloy), is preierablycoated over the copper coating to enhance the aonding operation. Thereinforcing alloy in molten form .s then poured into the coated shell.After allowing the somposite mold to cool, the laminated molding tool isremoved and is ready for molding operations without further treatment.The preferred alloy reinforcing mate- 'ial of the present inventioncontains an alloy of aluminum and zinc containing 20% by weight ofaluminum and has a melting point 896 and results in a supporting )Iback-up material for the nickel molding surface of extremely highcompressive strength. The fluidity of the above described alloy.however, is such that Where the resulting mold surface [S irregularlycontoured, the mateial may not completely till the nickel shell withouta great deal of mechanical manipulation. However, for relatively rlat orlevel molding surfaces, the alloy is quite suitable.

The following illustrative example is set forth, how- .:ver, it is to beunderstood that the invention is not imtted to the embodimentillustrated therein but rather is defined by the appended claims.

EXAMPLE The atlovs set forth in Table l were prepared accord- .ng toconventional techniques and employed as backing naterials forelectrot'ormed nickel shells as follows:

Eight nickel shells in the form of cups and tubes were :iectrotormedover a removable mandrel according to :onventronal methods. In four ofthe shells electroformed copper coatings were provided by conventionalmethods. The shel s were insulated and preheated in ovens totemaeratures rust below the melting points of the alloys listed .n Tablel. The interior of the shells were preliminarily :oated vtth a paste ofHandy Harmon Handy Flex, Type tliC, .1 liquid tlux mixtureconventionally employed for soldering of nickel and copper. Samples ofthe alloys listed in Table I were melted and poured into the shells atthe temperature indicated in Table I. A sample of each alloy was pouredinto both a nickel shell and a copper coated nickel shell.

Cu-Ni-Zu-P is a conventional backing alloy.

The mechanical properties of the cooled nickel shells containing thealloys of Table I are set forth in Table II.

TABLE II Compressive yield, Hardness, P RB Alloy:

(1) Cu-Zn-Ni-P 89 2) Al 5,000 (3) Al-Zn (20%) 50,000 80 (4) Al-Zn 35,000 75 (5) Al-Zn (30%) 41, 000 75 As is apparent from the results setforth in Tables I and II, the Al-Zn alloys of the present inventioncombine the best properties of melting point, strength and hardness.

The Cu-Zn-Ni-P alloy was found to be unsatisfactory as a backingmaterial as the degree of wetting was difficult to control. Either noWetting occurred or the nickel shell was locally consumed.

Machining of the compression specimens indicated that the alloys of theinvention are readily machineable to a high finish.

The resulting specimens were examined and mounted to form molds in ahydraulic press which was closed at about 80,000 pounds. Hot plexiglasswas forced into the molds at 25,000 p.s.i. to simulate injectionmolding.

Whereas the Cu-Zn-Ni-P alloy backed molds were deformed by the moldingoperation, Al-Zn alloys backed molds of the invention functionsatisfactorily and were not deformed by the compression and elevatedtemperatures endured during the molding operation.

The al oy of the present invention is readily machined and mountingholes can be drilled and tapped easily. The alloy does not gall or losethread shape with repeated insertion of screws or bolts. The back-upalloy permits repair welding of the nickel if it is dented or damaged inservice. Use of organic back-up material, used heretofore in some cases,does not permit such repair.

What I claim is:

1. A laminated molding tool comprising a molding surface layerintimately bonded to a thermally conducting supporting substrate, whichimparts rigidity and strength to said surface layer, said moldingsurface layer comprising nickel and said supporting substrate comprisingan alloy of aluminum and zinc wherein the amount of aluminum is in therange of from about 10% to about 30% by weight, based on the weight ofsaid alloy.

2. The molding tool of claim 1 having an interlayer of copper interposedbetween and intimately bonded to said molding surface layer and saidsupporting substrate.

3. The molding tool of claim 1 wherein said molding surface layercomprises electrodeposited nickel.

4. A male, laminated molding tool adapted for molding comprising amolding surface layer intimately bonded to a thermally conductingsupporting substrate which imparts rigidity and strength to said surfacelayer, said molding surface layer comprising electrodeposited nickel andsaid supporting substrate comprising an alloy of aluminum and zincwherein the amount of aluminum is in the range of from about 10% to 30%by weight and the amount of zinc is in the range of from about to aboutby weight.

5. The male molding tool of claim 4 having an interlayer of copperinterposed between and intimately bonded to said electrodeposited nickelmolding surface layer and said supporting substrate.

References Cited UNITED STATES PATENTS 627,289 6/1899 Bennett 724761,789,455 1/1931 SpaCkman 72-476 2,837,818 6/1958 Storeheim 29l943,044,156 7/1962 Whitfield 29197 3,046,640 7/1962 Singleton 29197 HYLANDBIZOT, Primary Examiner US Cl. X.R. 29--194, 197

